Perplexity is an information theory term, not a brand:

Perplexity of a probability model -- A model of an unknown probability distribution p, may be proposed based on a training sample that was drawn from p. Given a proposed probability model q, one may evaluate q by asking how well it predicts a separate test sample x1, x2, ..., xN also drawn from p.

https://en.wikipedia.org/wiki/Perplexity

Not how the law works. I’m not certain Perplexity has trademarked their name but the question of whether it’s an information theory term or not wouldn’t prevent them from doing so, nor would it prevent them from defending that trademark.

Engineer-y people trying to interpret law has to be one of the most reliably silly things on HN.

Have you ever tried to trademark a random noun?

No but lots of other people have: https://tmsearch.uspto.gov/search/search-results

Feel free to release a computer named Apple to prove me wrong.

Alright, read up on domains, then try arguing that 'perplexity' as company and noun are in different spaces! I grant you that if they were, the company could trademark that noun. But it seems clear that Perplexity named itself after the noun and by so doing gave up the option of trademarking its company name.

That doesn't mean in any way that it can't be a legal trademark.

I’m an IP lawyer & AI dev: my first reaction was, “hmm there are trademark issues here.” From a US perspective: “Perplexity” certainly CAN be a trademark, and the company has applied for one—to my knowledge it’s still pending. If the term was merely “descriptive” of the service provided, like “American Airlines”, then the company would need to show that the term has acquired distinctiveness: ie, that purchasers associate the term with that specific company. But perplexity is probably more than merely descriptive here.

Assuming that they have a valid trademark, the issue becomes whether there is a likelihood of confusion between Perplexity and Perplexica. That is a fact-specific, multifactor test, which I’ll spare you. But there could be arguments both ways IMO

EDIT: trademark issues aside, cool project!

HN is so incredible. The topic can be just about anything and there’s someone here with just the right expertise and/or set of skills to share their two pennies. The current topic is AI and IP law and here comes someone who’s an IP lawyer and AI engineer. I truly love this place.